Lawyers' Likelihoods

This paper explores whether lawyers can understand and apply the criminal burden of proof, and whether they are able to make the sort of likelihood estimates that the expert witness suggested would help the jurors in the case of R v Adams. The English Court of Appeal expressly rejected the use of mathematical formulae to determine guilt or innocence. With this kind of restraining judgment, it is important that lawyers should have a thorough and reliable grasp of probability. Results suggest that their areas of misunderstanding include not only problems in making coherent estimates of likelihood or probability, and then drawing logical inferences, but also difficulties with percentages and ratios, and even with the criminal and civil burdens of proof.